Ageing

Longevity genes - under normal circumstances some genes maufacture proteins that limit lifespan - can be mutated

Nematode roundworm

daf 2 gene - controls stage in worms life cycle

worms can hibernate

protein produced by daf 2 drives worms development

daf 2 genes similar in humans

Caloric restriction is shown to prolong life

After a number of divisions cells can no longer proliferate

Young human fibroblasts divide about 50 times - the Haylimit limit

at least 4 genes involved

Relicative senescence, we dont die because we run out of cells

Most senscene cells are not dead or dying

They respond to hormones and stimuli 

just cant proliferate

Telomeres- get shorter as cell divides repeated thousands of times

don't contain important genetic info

help keep chromosomes intact

During mitosis - replicates DNA can't the outer edges

each time the cell divides, the telomeres shorten

Over time the telomeres shorten so much that it leads the cell to stop proliferating

Telormer length give some indication of how many divisions cells has undergone and how many remain before it can duplicate

in immortal cancer cells telomeres act abnormally

no longer shrink with each division

Telomerase is inactive in most adults

swing into action in advanced cancers

if you block telomerase activity - cure cancer

Everyday metabolic processes exposed cells to biochemical substance

Oxygen radicals, heat shock, hormones

Oxygen radicals - demolish proteins and damage nucleotides

damage contributes to ageing

Free radical - highly reactive electron

by - products of normal metabolism

free radicals do not go unchecked

nutrients vitamins C and E and beta carotene

enzymes can prevent some oxidative damage

damage mounts and contributes to deterioating tissue

converts oxygen radicals into hydrogen peroxide which is then converted into O2 and H2O

non-enzymatic glycosation or glycation, glucose molecules attach themselves

sets in motion a chain of chemical reactions that end in the proteins binding together or crosslinking

Crosslinks = Advanced Glycosation end products (AGES) = toughen tissues and cause deterioation

Stiffen tissues, harden arteries, clouded eyes, loss of nerve functions

Macrophages combat glycation

eliminated by urine

produced when cells are exposed to various stress

triggered by exposure to toxic substances such as heavy metals

levels product depend on age

help the cell dissassembled dispose of damaged proteins

DNA can be damaged 'deletions, mutation'

ability to repair certain types of DNA damage is directly to life span

unprotected by the protein coat

Growth factors

substances such as Insulin - like growth factor

hormone injecting reverse ageing process - lean muscle mass

Recombinant Human Growth Hormone

synthetic version of pituatry gland

Production of testerone and oestrogen falls off

Hormone replacement

Oestrogen replacement lessens bone mass from menopause

DHEA - dehydroplandrosterone - abundant in youth

low levels associated with stress and cancer